Used in Historic Textiles by Means of Uv-Vis Spectrophotometry and Ft-Ir Spectroscopy

153

CHARACTERIZATION OF COLOURING COMPOUNDS IN ANNATTO (BIXA ORELLANA L.) USED IN HISTORIC TEXTILES BY MEANS OF UV-VIS SPECTROPHOTOMETRY AND FT-IR SPECTROSCOPY.

Dolores Julia Yusá-Marco1, María Teresa Doménech-Carbó1, Ivan Lucio Vaccarella1, Antonio Fernando Batista dos Santos1, Sofia Vicente-Palomino2 and Laura Fuster-López3 Instituto Universitario de Restauración del Patrimonio de la Universidad Politécnica de Valencia 1 Laboratorio de análisis físico-qímico y control medioambiental de obras de arte 2 Taller de materiales arqueológicos y etnográficos 3 Taller de análisis y actuación en pintura de caballete y retablos

CORRESPONDING AUTHOR: Dolores Julia Yusá-Marco, [email protected]

ABSTRACT: Valencian historic textiles were commonly woven with coloured silks and natural dyes in the 18th century. The optimisation of analytical methods to extract and classify the dyes used is required to understand not only their degradation process, but also the state of conservation of these textiles. This paper shows the results obtained in the optimisation of the preparation process of the two main colouring components in annatto (Bixa Orellana L.), namely, bixin and norbixin, prior to analysis by means of UV-Vis Spectrophotometry and FTIR spectroscopy. The results of the analysis were also satisfactor

KEYWORDS: natural Dyes, carotenoids, annatto, Bixa Orellana L, silk, FTIR spectroscopy, UV-Vis spectrophotometry

number of carotenoid compounds that constitute the main colouring 1. INTRODUCTION agents: bixin is the predominant colouring compound in liposoluble preparations, and its chemical structure is shown in Figure 1. Natural dyes obtained from plants, animals and minerals have been Norbixin (see also Figure 1), which can be obtained by means of historically combined according to ancient procedures and recipes bixin saponification, is the main colouring agent in hydrosoluble and have resulted in a wide spectrum of tones and shades. preparations. Nevertheless, norbixin can also be found in both seeds and liposoluble solutions. In the 18th century, dyes were classified into two groups according to their inherent characteristics and quality. The first group consisted Annatto colouring compounds can be identified by UV-Vis of the colourants considered ‘major or good dyes’ (‘tinte mayor o Spectrophotometry and FTIR Spectrometry. Devia developed bueno’), whereas the second group comprised dyes known as ‘minor an extraction method to determine the maximum absorption or false dyes’ (‘tinte menor o falso’). Those of the latter group were wavelength of annatto dyes. It consisted of 1gr of annatto dye seeds used “as base-dyes to obtain specific shades and also more affordable in a 100 ml-calibrated flask containing a 5% KOH solution. Then, mixtures. At other times, they were also used alone, but they were 1 ml aliquot of this solution was transferred to a second calibrated considered low-quality materials” (Roquero, 2006). flask (100 ml), which also contained a 5% KOH solution. The absorption spectrum finally obtained was in the range of between Annatto, the dye obtained from the Bixa Orellana L., was considered 300nm and 600nm (Figure 2). a “minor” dye. Joseph Macquer’s treatise refers to annatto as a weak material that changed and deteriorated easily. He also stated that “its Absorption bands with a maximum value at 450nm for the dye colours are so beautiful, and this is the only reason to use them since beauty is extracted from annatto (bixin) can be obtained as referred to in the preferred to duration when it comes to dyeing silks” (Macquer, 1771: 107). literature (Mosquera, 1989; Devia and Saldarriaga, 2003: 8 and Devia, 2005), and at 483 nm for norbixin (Natukolor, 2004). The UV- Given the beauty of the yellow and orange tones obtained with Vis spectrum of annatto was reported by Britton (Briton, 1995), which annatto, and despite being classified as a “minor” dye, it was widely is dominated by an absorption band with three maximum values. used for silk dyeing in Spain. Indeed, eighteenth-century textiles are a good example of this practice. Additionally, Devia developed the IR analysis of annatto dye seeds in the following way: pressed KBr powder is prepared with Dye treatises from the 18th century included a wide range of the coloured powder and the infrared spectrum is obtained (Devia, tones that could be obtained from annatto pure dye or diluted at 2005)). Devia indicates: “a band close to 1600 cm-1 can be observed that different concentrations. The combination of annatto with other represents the stretching vibration of the -C=O groups (typical of bixin colourants also produced all types of warm colours ranging from structures). Moreover, several consecutive bands can be observed in the area gold to maroon, which were reported in the treatises of that period between 1700 and 1800 cm-1, that are found typically in double bonds which (Fernández, 1995: 51). are usually present in the organic structures that characterise bixin” (Devia and Saldarriaga, 2003: 8). Annatto is a natural dye obtained from a tropical plant growing in America. Its seeds are covered by a red resin which contains a

ARCHÉ. PUBLICACIÓN DEL INSTITUTO UNIVERSITARIO DE RESTAURACIÓN DEL PATRIMONIO DE LA UPV - Núm. 3 - 2008 154 Dolores Julia Yusá-Marco, María Teresa Doménech-Carbó, Ivan Lucio Vaccarella, Antonio Fernando Batista dos Santos, Sofia Vicente-Palomino, Laura Fuster-López

Figure 1. Chemical structure of bixin and norbixin carotenoids, cis and trans isomers and Figure 2. UV-Vis spectrum of annatto extracts from solid dye seeds (Devia, 2005) their main degradation products (Scotter, 1995)

Extracting the colouring compounds from the fabric (silk in this case) out prior to the spectroscopic characterisation of annatto colouring prior to analysing by spectroscopic techniques is required to identify compounds. Two types of extraction processes have been evaluated. natural dyes in historic textiles. Thus, several methods have been The first method was carried out in two stages: acid hydrolysis proposed for this purpose. Among them, it is worth mentioning that followed by extraction with organic solvents. The second method is of Orska-Gawrys et al (2003: 239), which uses a mixture of ethanol simpler than the first, and consists of direct extraction with organic and hydrochloric acid for the hydrolysis stage. Chloro-solvents such solvents without the need for a previous acid hydrolysis stage. as dichloromethane can be used for direct extraction, as suggested by Tocchini and Mercadante (2001: 310). Other authors, however, Secondly, the colouring compounds extracted from the dyed propose the use of dimethylformamide and acetic acid for the direct textiles were characterised by UV-Vis Spectrophotometry and extraction of synthetic dyes from cotton fibre (Chao et al, 1998: 59). FTIR spectrometry. The assignment of the main absorption bands in the UV-Vis-IR regions allowed us to not only differentiate the Being a proteinaceous material, silk can be affected by acid or basic different colouring compounds present in the dyed textiles, but to environments that deteriorate it as a result of the hydrolysis process. also evaluate the efficiency of the extraction method tested. The typical functional groups contained in their amino acids, which are present in the coloured extracted solution, can be identified by 2. EXPERIMENTAL FTIR. 2.1. Reagents and Reference Materials As Becker states: “Over 80% of the fibroin molecule consists of glycine, alanine and serine in a 3:2:1 ratio. The highly repetitive sequence of fibroin The chemical reagents and solutions used were ethanol, 96%, pa, is described by: Gly-Ala-Gly-Ala-Gly-Ser-Gly-Ala-Ala-Gly- [Ser-Gly-(Ala- Panreac; hydrochloric acid, 37%, pa, Carlo Erba; Dichloromethane Gly) -]8-Tyr, where n is usually 2”. (Becker et al, 1997:27). The chemical n (DCM), pa, Carlo Erba; Chloroform, 99+%, Acros; Ethanol: structure of these amino acids is characterised by the existence of hydrochloric acid 3M (1:1) solution. Acetonitrile (ACN) and Methanol primary amides. (MeOH), HPLC-gradient grade, Carlo Erba; Potassium bromide, 99+%, RS, Aldrich; Trifluoroacetic acid (TFA) 99% (Panreac); Seok Ki et al. developed the structural characterisation of silk by Acetic acid 100% (Prolabo), Dimethylsulfoxide (DMSO), RS, Carlo means of several analytical techniques such as FTIR: “Protein Erba, Deionised water, HPLC grade, Medica Elga (Eolia Water). HCl conformation is determined by identifying the peak positions of amide I, II, 3M:MeOH:H O (2:1:1) solution and MeOH:H O (1:1) solution and III corresponding to C=O, N-H, and C-N stretching, respectively. All 2 2 regenerated silk filaments present amide I and II peaks at around 1630 and Annatto seeds (ref. 37350) were provided by Kremer pigmente 1520 cmí1, as well as an amide III peak at 1260 cmí1 as a shoulder peak, thus (Figure 3). indicating the ȕ-sheet structure known as silk II type. On the other hand, SS powder presents amide I and II peaks at slightly different positions (1623 and The experiments were performed on 100% silk, whose commercial 1516 cmí1) with the absence of a shoulder peak at 1260 cmí1. This is probably name was ponge textile, supplied by Soditex, S.L.. This textile was due to an aggregation of SS molecules, and not to ȕ-sheet conformation.” characterised (Vicente-Palomino et al, 2006: 139) as: (Seok Ki et al, 2007: 346) 2.2. Instrumentation This research shows the earliest results obtained in the optimisation of the extraction process of the two main colouring components of UV-Vis Spectrophotometry. The spectra in the UV and visible region annatto, bixin and norbixin, from silk textiles which was carried were measured with a HITACHI U2010 recording double-beam

Number of yarns Density (taffeta) Name Composition Fabric grammage warp weft warp weft Pongee 100% Silk 7 tex 4 tex 60 60 0’00459g/m2

Table 1 Characterization of textile.

ARCHÉ. PUBLICACIÓN DEL INSTITUTO UNIVERSITARIO DE RESTAURACIÓN DEL PATRIMONIO DE LA UPV - Núm. 3 - 2008 Characterization of colouring compounds in Annatto (Bixa Orellana l.) Used in historic textiles by means of UV-VIS spectrophotometry and FT-IR spectroscopy 155

Figure 3. Annatto seeds. )LJXUH899LVVSHFWUDRIVDPSOHV$&+& DQG7 FRUUHVSRQGLQJWRWKHG\H extracted from 50 µL of dyeing bath and 0.0023g of dyed silk, respectively, obtained by means of the acid hydrolysis-dichloromethane extraction procedure spectrophotometer. The work conditions were: a spectral range of 200- 1000 nm, a scan speed of 800 nm.min-1, a sampling interval of 1 nm, a slit width of 2 nm and a path length of 10 mm. Data were processed with UV Solutions software version 1.2. (HITACHI INSTRUMENTS, Inc.).

FTIR Spectroscopy. IR absorption spectra were performed in the attenuated total reflectance mode (ATR) with a Vertex 70 Fourier transform infrared spectrometer (BRUKER OPTIK GmbH) with an FR-DGTS (fast recovery deuterated triglycine sulphate) temperature- stabilised coated detector made by BRUKER OPTICS® with an MKII Golden Gate Attenuated Total Reflectance (ATR) accessory. Number of co-added scans: 32; resolution: 4 cm-1. Data were processed with the OPUS software, version 5.0.

2.3. Procedures

2.3.1. Preparation of reference materials Aqueous extracts of the colouring compounds from annatto seeds were used for the dyeing procedure. Non-mordanted silk was then immersed in the dye bath. Figure 5. UV-Vis spectrum of sample T00 corresponding to 0.0055g dyed silk without mor- dent obtained by means of the direct extraction procedure using 40µL DMF:acetic acid.

2.3.1.1. Preparation of the dyeing baths Forty grams of annatto seeds were soaked in 200 mL of deionised 2) Direct solvent extraction water for 20 h at room temperature, and were then heated at 90ºC for 20 minutes. The hot solution was filtered using a nylon filter, a) Extraction was performed by adding an organic solvent, 60µL resulting in a concentrated dyeing bath (1C). This solution was then chloroform, or diluted to 600 mL in order to obtain that a dyeing bath (ACH-1C). b) 60 µL DMF: acetic acid (9:1). 2.3.1.2. Dyeing of silk textiles Wetted and unmordanted silk was immersed in the dyeing solution Experimental measurements (ACH-1C) at 80ºC for 2h. After cooling the dyeing solution, the dyed 50 µL yellow extract were placed into a quartz microcell and a UV- silk (T00) was rinsed in deionised water and left to dry in the dark. Vis spectrum was obtained. 50 µL yellow extract were gently added into 0.1mg of f inely powdered 2.3.2. Extraction Methods and dried (at 100ºC for 2 hours) KBr. The IR spectra were obtained Following a series of prior experiments, we propose three procedures in the ATR mode from the measurements performed on the dyed to extract the colouring compounds from the textiles and the dyeing KBr powder obtained after evaporating the solvent. bath. 3. RESULTS AND DISCUSSION 1) Acid hydrolysis and organic solvent extraction 3.1. UV-Vis Spectrophotometry a) 50µL of the dyeing solution (ACH-1C), or 1.5-2.5mg of the dyed silk textiles (T00), were hydrolysed by adding 40µL of (1:1) The absorption spectrum obtained from the dyeing bath (ACH-1C) HCl:EtOH solution for 15 minutes at 100ºC. Afterwards, 60µL and the dyed silk (T00) by means of the above-mentioned Extraction dichloromethane were added and two phases were obtained. The Method 1-a (acid hydrolysis - solvent extraction) is shown in Figure yellow extract formed in the organic phase was then analysed. 4, whereas the absorption spectrum obtained from the dyed silk (T00) by means of Method 2 using DMF: Acetic acid is shown in b) A second extraction with 50µL H O was carried out on the former 2 Figure 5. yellow extract, and 120µL of HCl:EtOH solution (1:1) and 100µL of dichloromethane were used in the first and second steps.

ARCHÉ. PUBLICACIÓN DEL INSTITUTO UNIVERSITARIO DE RESTAURACIÓN DEL PATRIMONIO DE LA UPV - Núm. 3 - 2008 156 Dolores Julia Yusá-Marco, María Teresa Doménech-Carbó, Ivan Lucio Vaccarella, Antonio Fernando Batista dos Santos, Sofia Vicente-Palomino, Laura Fuster-López

Figure 6. IR spectrum of annatto extracts from solid dye seeds. Figure 7. FTIR spectra of ponge silk and annatto dyeing bath extract by Method 1a.

The IR spectra of the pongee silk samples and the dyeing bath obtained by Method 1a are presented in Figure 7. We observe a significant decrease in the absorption values of the IR bands if we compare them with the spectrum obtained from the annatto seeds. On the other hand, the IR absorption ranges typically found in the amino acids contained in the chemical structure of silk are shown in Figure 1, as indicated by both Becker and Seok Ki (Becker et al, 1997: 27 and Seok Ki et al, 2007: 346)

The IR spectra of the dyed silk, T00, obtained by Methods 1a (Figure 8) and 1b, are shown. Typical annatto bands can be seen in both spectra. They exhibit a broad band at 3388 and 3465 cm-1 absorbed to the stretching vibration of the OH groups and to the sharp bands from C=O to 1705 and 1721 cm-1 absorbed to stretching, C-O to 1285- 1145 cm-1 and 1288-1158cm-1 (stretching), C=C to 1641-1611cm-1 and 1631-1613cm-1 (stretching, alkenes), respectively. Despite the bands not being as sharp as those obtained from the dying solution, the confirmation of the dye concentration in the dyed silk is lower than its concentration in the dyeing solution. Furthermore the additional Figure 8. IR absorption spectrum of sample T00 corresponding to the dyed silk (0.0013g) water extraction stage equally contributes to a noticeable dilution obtained by 40µL EtOH:HCl - 60µL Dichloromethane (Method 1a). of the dye. Therefore, we suggest that Method b) is not a suitable extraction method.

The UV-Vis spectrum in Figure 5 corresponding to dyed silk using The main IR absorption bands identified by Method 1a in samples Extraction Method 2 displays absorption values at 495, 464 and 438 extracted from the silk specimens, the annatto solid seeds, the dyeing nm. This result matches that of Britton (1995), and shows that it is solution (ACH-1C) as well as from dyed silk (T00) are shown in Table possible to discriminate among three maximum absorption values 1. If we observe the sample corresponding to the T00 dyed silk, both IR for annatto extracts unlike those obtained by Mosquera (1989) and bands are typically found in annatto dyes (3388 and 1611 cm-1), while Devia (2003 and 2005). The UV-Vis spectra depicted in Figure 4 those corresponding to the silk (1705, 1513 and 1454 cm-1) may also be correspond to the colouring compounds extracted from both the identified. This is a direct result of the extracting method of the dyed dyeing bath and the dyed silk samples using Method 1-a, which are silk specimen where the protein structure of silk is also hydrolysed by similar to those in Figure 5 where the maximum absorption values hydrochloric acid. Consequently, it can be said that this extraction at 493-6, 461-4 and 435-9 nm appear. Satisfactory results were method highlights the bands corresponding to the silk itself together obtained by both extraction methods. with those corresponding to the coloured compounds.

3.2. FTIR Spectroscopy The literature suggests a direct extraction method with chloroform (Souza, 2005). This led us to develop Method ‘c’. The IR spectra The main frequencies of the absorption bands, relative intensities obtained by a direct extraction with chloroform (Method ‘c’) from and tentative assignments are provided in Table 1 for the annatto both the dyeing solution (ACH-1C) and dyed silk (T00) reveal a extracts from solid dye seeds, silk, the dyeing bath and dyed silk. broad band at 3349 cm-1 absorbed to the stretching vibration of the OH groups, as well as a band at 1716 cm-1 absorbed to a stretching The IR spectrum obtained from the solid finely powdered annatto vibration of the C=O group, 1285-1159cm-1 to a stretching vibration seeds is shown in Figure 6. This spectrum displays a broad band at of C-O, and a band at 1610 cm-1 to a stretching vibration of C=C -1 3284 cm which is ascribed to the stretching vibration of the OH group. As seen, direct extraction is more effective when performed -1 groups and to 2920 and 2855 cm associated with the stretching in the dyeing solution than in the dyed silk sample since sharper vibrations of the hydrocarbon skeleton, as well as with sharp bands bands are obtained. at 1721, 1603, 1149 and 962 cm-1 whose assignment is summarised in Table 1. These absorption bands are typical of carotenoid At this point, it is interesting to show the comparison between the compounds, in particular bixin. two organic solvents used in Method ‘c’; chloroform and DMF:acetic acid; applied to the dyed silk T00 extraction. The IR spectra are

Table 2. The main IR absorption bands identified in the samples of extracts from silk, solid annatto seeds, dyeing bath (ACH-1C) and dyed silk (T00) by Method 1a. obtained by direct extraction with chloroform and DMF:acetic acid from the dyed silk T00. Both organic solvents can extract coloured Valencia PAID-06-06 Project 20070325 (Cod.4720) and PAID-08- compounds from dyed silk. However DMF:acetic acid extraction 07 (Acciones Especiales) are gratefully acknowledged. The authors and absorption present sharper and larger bands which may be wish to also acknowledge the Museum Conservation Institute for caused by the acid hydrolysis that took place during the procedure. loaning equipment. 4. CONCLUSIONS LEONARDO DA VINCI Community Programme (European Union Council Decision 1999/382 CE), Progetto P.A.G. (Overseas Placements In the 18th century, Valencian historic textiles were commonly made of Graduates) proposed by the Università di Palermo. out of coloured silks and used a variety of natural dyes. The annatto natural dye (obtained from Bixa Orellana L) was particularly popular Finally, the grant to D. Antonio Fernando Batista Dos Santos, funded at that time. Dye extractions, as well as UV-Vis Spectrophotometry by the PhD Scholarship Programme of the Ministério da Educação - and FTIR Spectroscopy analyses, have worked well according to Brazil - Geld- CAPES (Coordenação de Aperfeiçoamento de Pessoal their chemical characterisation. de Nivel Superior)-IPHAN (Instituto do Patrimonio Histórico e Artístico Nacional), is also acknowledged. A two-stage extraction process (firstly acid hydrolysis and then organic solvent extraction with dichloromethane) proved to be a BIBLIOGRAPHY suitable procedure to analyse natural dyes from historic silk textiles as evidence of early results. Annatto-dyed silk was also analysed Becker, M.A., Magoshi, Y., Sakai, T., Tuross, N.C. (1997): “Chemical and by UV-Vis Spectrophotometry and FTIR Spectrometry. Satisfactory physical properties of old silk fabrics”, Studies in Conservation, 42 27-37 results were obtained since the analytical signal was obtained at a visible range spectrum. FTIR has helped identify the chemical Britton, G., Liaaen-Jensen, S., Pfander, H. (1995): Carotenoids 1B:Spectroscopy, structure of the extracted annatto corresponding to the carotenoid Birkhauser Verlag, Germany. compounds. Chao, Y.C., Chung, Y.L., Lai, C.C., Liao, S.K. and Chin, J.C. (1998): Additionally, these results provide more in-depth knowledge of not “Dyeing of cotton-polyester blends with anthraquinonoid vat dyes”, Dyes only the behaviour of dyes and dyed textile fibres, but also of their and Pigments, 40 59-71 detection and identification in textiles. Devia-Pineda, J.E., Saldarriaga-Calderón, L. (2003): “Planta piloto para ACKNOWLEDGEMENTS obtener colorante de la semilla del achiote (Bixa Orellana, L.), Revista Universidad EAFIT (Colombia), 8-22 FFinancial support from the Valencian Regional Government “R+D Generalitat Valenciana” GV/2007/212 and the Research and Devia-Pineda, J.E. (2005): Tesis doctoral titulada Pulverización de colourantes Development Support Programme of the Polytechnic University of naturales por secado por atomización, Universidad EAFIT, Colombia.

ARCHÉ. PUBLICACIÓN DEL INSTITUTO UNIVERSITARIO DE RESTAURACIÓN DEL PATRIMONIO DE LA UPV - Núm. 3 - 2008 158 Dolores Julia Yusá-Marco, María Teresa Doménech-Carbó, Ivan Lucio Vaccarella, Antonio Fernando Batista dos Santos, Sofia Vicente-Palomino, Laura Fuster-López

Fernández, L. (1995): Tratado instructivo y práctico sobre el arte de la tintura. Reglas and Trojanowicz, M. (2003): “Identification of natural dyes in archeological experimentales y metódicas para tintar sedas, lanas, hilos de todas clases, y esparto en Coptic textiles by liquid chromatography with diode array detection”, Journal rama., Ed.Roig Impresores, Madrid. of Chromatography A, 989 239-248

Macquer, P.J. (1771): Arte de la tintura de sedas, Ed. Roig Impresores, Madrid. Roquero, A. (2006): Tintes y tintoreros de América-Catalogo de materias primas y registro etnográfico de México y centro América, Andes centrales y selva Amazónica, Mosquera, P. (1989): Factibilidad técnica e Industrial de la extracción de colourante Madrid: Ministerio de Cultura. del Achiote, Trabajo de grado (Ingeniero Químico). Universidad de Antioquía. Facultad de Ingeniería. Medellín Seok Ki, Ch., Wook Kim, J., Jin Oh, H., Hoon Lee, K., Hwan Park, Y. (2007): “The effect of residual silk sericin on the structure and mechanical NATUKOLOR S.A. (2004). “colourante de Bixina soluble en agua”. http:// property of regenerated silk filament.”, International Journal of Biological www.natukolor.com/bixina1.html. Macromolecules 41 346–353

Scotter, M.J. (1995): “Characterization of the Coloured Thermal Degradation Tocchini, L. y Mercadante, A.Z. (2001): “Extraçao e determinaçao, por Products of Bixin from Annatto and a Revised Mechanism for their CLAE, de Bixina e Norbixina em colouríficos”, Cienc.Tecnol.Aliment., formation”, Food Chemistry, 53(2) 177-185 Campinas, 21(3) 310-313

Souza de Oliveira, J. (2005): Caracterização, extração e purificação por cromatografia Vicente-Palomino, S., Bonet-Aracil,M.A., Arbués-Fandos, N. and Monllor- de compostos de urucum (Bixa orellana L.), Tesis doctoral en Ingeniería Química, Pérez, P. (2006): “Fabrics Analysis and characterization that usually are used Universidade Federal de Santa Catarina in the textile consolidation”. Arché. Publicación del Instituto Universitario de Restauración del Patrimonio de la UPV, 1 139-144 Orska-Gawrys, J., Surowiec, I., Kehl, J., Rejniak, H., Urbaniak-Walczak, K.

Versión española

TITULO: Caracterización de los componentes coloreados del achiote utilizado en los tejidos históricos valencianos mediente Espectrofotometría UV-Vis y Espectrometría FTIR.

RESUMEN: Los tejidos históricos valencianos del siglo XVIII fueron fabricados con seda teñida con colorantes naturales. Optimizar los métodos analíticos de extracción y caracterización de los colorantes naturales es necesario para comprender los procesos de degradación y por tanto, de conservación de estos tejidos. En este artículo se presentan los resultados obtenidos de la optimización de los procesos de extracción y caracterización mediante Espectrofotometría UV-Vis y Espectrometría FTIR de los dos componentes coloreados del achiote (Bixa Orellana L.), denominados bixina y norbixina. Los resultados obtenidos han sido satisfactorios.

PALABRAS CLAVES: tintes naturales, achiote, Bixa Orellana, Espectrometría FTIR, eEspectrofotometría UV-Vis, seda, carotenoides

ARCHÉ. PUBLICACIÓN DEL INSTITUTO UNIVERSITARIO DE RESTAURACIÓN DEL PATRIMONIO DE LA UPV - Núm. 3 - 2008